The present disclosure is generally related to phase change inks. More specifically, the present disclosure is directed to hot melt or phase change inks suitable for use in ink jet printing processes including piezoelectric ink jet printing processes, acoustic ink jet printing processes, and the like. One embodiment of the present disclosure is directed to a phase change ink composition comprising a colorant and an ink vehicle, the ink vehicle comprising a compound of the formula

wherein R1, R2, R3 and R4 are each independently selected from an alkyl group, including substituted alkyl groups, unsubstituted alkyl groups, linear alkyl groups, and branched alkyl groups, and wherein hetero atoms either may or may not be present in the alkyl group, the alkyl group having from about 1 to about 30 carbon atoms, an alkylaryl group, including substituted alkylaryl groups, unsubstituted alkylaryl groups, linear alkylaryl groups, and branched alkylaryl groups, and wherein hetero atoms either may or may not be present in the alkyl portion of the alkylaryl group or the aryl portion of the alkylaryl group, the alkylaryl group having from about 4 to about 30 carbon atoms, an arylalkyl group, including substituted arylalkyl, unsubstituted arylalkyl groups, linear arylalkyl groups, and branched arylalkyl groups, and wherein hetero atoms either may or may not be present in the aryl portion of the arylalkyl group or the alkyl portion of arylalkyl, the arylalkyl group having from about 4 to about 30 carbon atoms, or hydrogen, wherein R1, R2, R3 and R4 can be the same or different, provided that both R1 and R2 cannot both be hydrogen and R3 and R4 cannot both be hydrogen;
wherein X is selected from carbon, silicon, oxygen and nitrogen atoms, i is an integer between from about 3 to about 50, Yj and Y′j′ are each independently selected from carbon, silicon, oxygen and hydrogen atoms, j is an integer between from about 1 to about 50, j′ is an integer between from about 1 to about 50, and the ratio of ΣXi/ΣYjY′j′ for all non-hydrogen atoms attached to X is from about 0.1 to about 1.5;
wherein in various embodiments said ink exhibits a melt temperature of about 35° C. to about 120° C., a complex viscosity of less than about 100 Poise at a jetting temperature of no more than about 140° C., a viscosity of from about 1 to about 10,000 Centipoise, or from about 2 to about 20 Centipoise, or from about 5 to about 14 Centipoise at a jetting temperature of no more than about 140° C., and exhibits a Modulus at 25° C. of greater than about 0.1 GPa, about 0.1 to no more than about 4 GPa.
In general, phase change inks (sometimes referred to as “hot melt inks”) are in the solid phase at ambient temperature, but exist in the liquid phase at the elevated operating temperature of an ink jet printing device. At the jet operating temperature, droplets of liquid ink are ejected from the printing device and, when the ink droplets contact the surface of the recording substrate, either directly or via an intermediate heated transfer belt or drum, they quickly solidify to form a predetermined pattern of solidified ink drops.
Phase change inks for color printing typically comprise a phase change ink carrier composition which is combined with a phase change ink compatible colorant. In a specific embodiment, a series of colored phase change inks can be formed by combining ink carrier compositions with compatible subtractive primary colorants. The subtractive primary colored phase change inks can comprise four component dyes, namely, cyan, magenta, yellow and black, although the inks are not limited to these four colors. These subtractive primary colored inks can be formed by using a single dye or a mixture of dyes. For example, magenta can be obtained by using a mixture of Solvent Red Dyes or a composite black can be obtained by mixing several dyes. U.S. Pat. No. 4,889,560, U.S. Pat. No. 4,889,761, and U.S. Pat. No. 5,372,852, the disclosures of each of which are totally incorporated herein by reference, teach that the subtractive primary colorants employed can comprise dyes from the classes of Color Index (C.I.) Solvent Dyes, Disperse Dyes, modified Acid and Direct Dyes, and Basic Dyes. The colorants can also include pigments, as disclosed in, for example, U.S. Pat. No. 5,221,335, the disclosure of which is totally incorporated herein by reference. U.S. Pat. No. 5,621,022, the disclosure of which is totally incorporated herein by reference, discloses the use of a specific class of polymeric dyes in phase change ink compositions.
Phase change inks have also been used for applications such as postal marking, industrial marking, and labeling.
Phase change inks are desirable for ink jet printers because they remain in a solid phase at room temperature during shipping, long term storage, and the like. In addition, the problems associated with nozzle clogging as a result of ink evaporation with liquid ink jet inks are largely eliminated, thereby improving the reliability of the ink jet printing. Further, in phase change ink jet printers wherein the ink droplets are applied directly onto the final recording substrate (for example, paper, transparency material, and the like), the droplets solidify immediately upon contact with the substrate, so that migration of ink along the printing medium is prevented and dot quality is improved.
Compositions suitable for use as phase change ink carrier compositions are known. Some representative examples of references disclosing such materials include U.S. Pat. No. 3,653,932, U.S. Pat. No. 4,390,369, U.S. Pat. No. 4,484,948, U.S. Pat. No. 4,684,956, U.S. Pat. No. 4,851,045, U.S. Pat. No. 4,889,560, U.S. Pat. No. 5,006,170, U.S. Pat. No. 5,122,187, U.S. Pat. No. 5,151,120, U.S. Pat. No. 5,372,852, U.S. Pat. No. 5,496,879, European Patent Publication 0187352, European Patent Publication 0206286, German Patent Publication DE 4205636AL, German Patent Publication DE 4205713AL, and PCT Patent Application WO 94/04619, the disclosures of each of which are totally incorporated herein by reference. Suitable carrier materials can include rosin esters, polyamides, dimer acid amides, fatty acid amides, epoxy resins, fluid paraffin waxes, fluid microcrystalline waxes, Fischer-Tropsch waxes, polyvinyl alcohol resins, polyols, cellulose esters, cellulose ethers, polyvinyl pyridine resins, fatty acids, fatty acid esters, polysulfonamides, benzoate esters, long chain alcohols, phthalate plasticizers, citrate plasticizers, maleate plasticizers, sulfones, polyvinyl pyrrolidinone copolymers, polyvinyl pyrrolidone/polyvinyl acetate copolymers, novalac resins, natural product waxes, mixtures of linear primary alcohols, and linear long chain amides, and mixtures of linear primary alcohols and fatty acid amides, and liquid crystalline materials.
Molecules capable of self-assembly through hydrogen bonding are known. For example, in “Reversible Polymers Formed from Self-Complementary Monomers Using Quadruple Hydrogen Bonding,” R. P. Sijbesma et al., Science, Vol. 278, p. 1601 (1997), the disclosure of which is totally incorporated herein by reference, discloses the use of units of 2-ureido-4-pyrimidone that dimerize strongly in a self-complementary array of four cooperative hydrogen bonds as the associating end group in reversible self-assembling polymer systems. The unidirectional design of the binding sites prevent uncontrolled multidirectional association or gelation. Linear polymers and reversible networks were formed from monomers with two and three binding sites, respectively. The thermal and environmental control over lifetime and bond strength made many properties, such as viscosity, chain length, and composition, tunable in a way not accessible to traditional polymers. Hence, polymer networks with thermodynamically controlled architectures could be formed for use in, for example, coatings and hot melts, where a reversible, strongly temperature-dependent rheology is highly advantageous.
U.S. Pat. No. 6,320,018, entitled “Supramolecular Polymer,” the disclosure of which is totally incorporated by reference herein, describes in the abstract thereof a polymer comprising monomeric units linked via 4H-bridges and bound within said polymer via a different bond. The bond via the H-bridges is much stronger than with known supramolecular polymers.
U.S. Pat. No. 6,906,118 entitled “Phase Change Ink Compositions,” the disclosure of which is totally incorporated by reference herein, describes in the Abstract thereof a phase change ink composition comprising a phase change ink composition comprising a colorant and an ink vehicle, the ink being a solid at temperatures less than about 50° C. and exhibiting a viscosity of no more than about 20 centipoise at a jetting temperature of no more than about 160° C., wherein at a first temperature hydrogen bonds of sufficient strength exist between the ink vehicle molecules so that the ink vehicle forms hydrogen-bonded dimers, oligomers, or polymers, and wherein at a second temperature which is higher than the first temperature the hydrogen bonds between the ink vehicle molecules are sufficiently broken that fewer hydrogen-bonded dimers, oligomers, or polymers are present in the ink at the second temperature than are present in the ink at the first temperature, so that the viscosity of the ink at the second temperature is lower than the viscosity of the ink at the first temperature.
While known compositions and processes are suitable for their intended purposes, a need remains for phase change inks that are suitable for hot melt ink jet printing processes, such as hot melt piezoelectric ink jet processes and the like. In addition, a need remains for phase change inks that are suitable for hot melt acoustic ink jet printing processes. Further, a need remains for low melt temperature phase change inks having low viscosity values at the jetting temperature of a hot melt ink jet printer. Further, a need remains for a low melt temperature phase change ink that is adequately hard so as to not be easily scratched off the paper and appropriately flexible so as to not fracture when the paper is folded. Previously known materials described in U.S. Pat. No. 6,320,018 exhibit, during cooling, a gradual increase in viscosity and produce, after a few hours at room temperature, a brittle solid similar to typical thermoplastic polymers. While such materials are suitable for their intended purposes, there remains a need for a phase change ink composition capable of generating supramolecular polymers with controllable melt temperatures, viscosities, while maintaining an adequate elastic modulus based on the designed intrinsic molecular structure.
The appropriate components and process aspects of the each of the foregoing may be selected for the present disclosure in embodiments thereof.